南沙海区曾母盆地地层系统

The Stratigraphic System of the Zengmu Basin,Southern South China Sea

曾母盆地是南沙海区研究和勘探程度较高的盆地,其地层系统一直是建立整个南沙海区地层系统的重要依据.然而由于盆地沉积厚度大和横向相变快等原因,对曾母盆地的分层方案和地层时代的认识存在很大分歧.为了给曾母盆地甚至南沙海区的油气勘探中地层划分对比和地震剖面的解释提供基础依据,在搜集整理和分析国外有钻井控制的地震剖面和分层方案的基础上,提出了一个实用的、便于与南海北部盆地对比的曾母盆地地层划分对比方案.将中海油对南海北部诸盆地制定的一套地层界面编号系统和地矿部广州海洋地质局对曾母盆地地层的命名结合起来,并根据国外在曾母盆地获得的钻探和联井地震测线资料对界面的时代作了一定调整,将曾母盆地基底以上的地层划分为4组1群(曾母组、立地组、海宁组、南康组、北康群),之间由5个重要不整合面(Tg、T60、T40、T32、T30)相分隔.还将该方案与国内外其他方案进行了对比和讨论,以供阅读有关资料时参考.为了方便将这套地层系统应用于地震剖面的解释和分析,用实例显示了同一地层中由于地层相变而造成的地震相的巨大变化,以及各重要不整合面的特征及其在地震剖面上的表现.

The Zengmu basin is a well-studied hydrocarbon-bearing basin in the Nansha area of the southern South China Sea.The stratigraphic system of the Zengmu basin has been an important element for building regional stratigraphic system.However,the large thickness and quick changes of the strata facies have made it difficult and controversial to divide and date the basin.In order to provide basis for stratigraphic division and correlation in hydrocarbon exploration,we analyze existing data from wells and seismic profiles as well as proposed stratigtraphic columns,and propose a stratigraphic system that is comparable with that used in the exploration of the northern South China Sea.This system combines the numbering system of the CNOOC and the nomenclature of the GMGS,and date the stratigraphic boundaries with existing wells and cross-well seismic profiles.The strata above the basement are divided into four formations and one group（the Zengmu,Lidi,Haining,and Nankang Formations,and the Beikang Group）,which are bottomed by five unconformities（Tg,T60,T40,T32,and T30）.In order to facilitate the application of this stratigraphic system,the comparison of this scheme with other schemes is also presented,and facies changes within a formation and characteristic unconformities between formations are demonstrated by seismic profiles.